1. Field of the Invention
The present invention relates to an optical fiber amplifier and an amplification method for compensating dispersion and loss of an optical signal, and more particularly, to an optical fiber amplifier capable of compensating dispersion and loss of an optical signal in transmission thereof and an amplification method for compensating dispersion and loss of an optical signal using the same.
2. Description of the Prior Art
Data traffic is exponentially increasing owing to the Internet, which is implemented in part with a high Wavelength Division Multiplexing (WDM) optical communication network to accommodate the increase. The latter may be accomplished by increasing the number of transmission channels or by raising the transmission rate per channel. When the transmission rate per channel of the optical signal reaches or exceeds a gigabit per second, the optical signal becomes especially sensitive to the effect of dispersion and may require compensation. One well known method utilizes a Dispersion Compensating Fiber (DCF) having negative dispersion to compensate for positive dispersion occurring in an optical signal.
Use of a DCF to compensate for dispersion of an optical signal results in a large amount of power loss and therefore requires implementation with an additional optical amplifier. The optical transmitter may include, for example, an Erbium-Doped Fiber Amplifier (EDFA). A Raman Amplifier is also widely used for this purpose.
The EDFA applies a pump signal, i.e., a pumped optical signal, to an optical fiber which is doped with the element erbium, in order to directly amplify a received optical signal without having to convert the optical signal into an electric signal. The Raman amplifier uses an optical fiber which serves as a nonlinear medium for generating a scattered pump signal from an incident non-chromatic pump signal to amplify an optical signal.
When the EDFA is used to compensate power loss of an optical signal owing to the DCF, more EDFAs are needed, in proportion to the transmission distance for the optical signal, thereby degrading the Optical Signal Noise Ratio (OSNR). Also, incorporating a DCF and a number of EDFAs into one module disadvantageously increases the volume of the module.
Although use of the Raman amplifier can improve OSNR, the efficiency of Raman amplification is lowered. As a result, a pump Laser Diode (LD) is required to input a high-power pump signal into the optical fiber to obtain a predetermined, suitable level of gain.